1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
In recent years, there has been known an image forming apparatus having a paper feed unit for separating paper sheets stacked in a paper feed tray from each other to carry the paper sheets one by one using air suction force.
For example, JP-A-07-101579 discloses a sheet feeding device including a sheet adhering unit for sucking air using air suction force so that each sheet adheres to a conveying unit; the conveying unit for carrying each sheet; an adhering preventing air spraying unit for spraying air on a tip of each sheet which adhered to the conveying unit; and an air adjusting unit for increasing or decreasing the quantity of air from the adhering preventing air spraying unit during sheet feeding. This sheet feeding device can prevent a next sheet from adhering to the conveying unit while carrying a previous sheet.
JP-A-10-315556 discloses a sheet feeding device including a floating unit for spraying air on stacked sheets to float each of the sheets; a suction unit for sucking air using air suction force so that each floated sheet adheres to a conveyor belt; a plurality of paper feed units each having a first air passageway through which the air to be supplied to the floating unit passes and a second air passageway through which the air from the suction unit passes; and an blower unit communicated with the first and second air passageways of each of the paper feed units to generate air for spraying and air for suction. The size or paper weight of each sheet stacked on a sheet stack unit is limited according to a distance from the blower unit to the paper feed unit.
JP-A-2001-80750 discloses a method of presetting a paper feed unit in which a preset table storing preset quantities which are set on the basis of paper quality data is created and a preset quantity corresponding to an input value of paper quality data is selected from the preset table. The paper quality data includes a paper type, a paper weight, a paper size and a paper texture. Examples of preset quantities include a supply quantity of air in separating paper sheets in a paper storage unit from each other by air, a supply quantity of air in stripping the paper sheets from the paper storage unit one by one, and a vacuum pressure of a vacuum adhering unit by which a paper sheet adheres to a feeder for conveyance.
In an image forming apparatus having a feeding device as shown in JP-A-7-101579 or JP-A-10-315556, however, a user has to manually configure a setting value such as an air flow quantity or a wind pressure for each paper feed unit as needed when changing the setting values which are preset in the feeding device. Therefore, even when the same type of paper sheets are stacked in a plurality of paper feed trays, the setting value must be manually changed for each paper feed tray, that is, for each paper feed unit. This could be a troublesome work.
An image forming apparatus having a function as disclosed in JP-A-2001-80750 is capable of selecting a setting value corresponding to a type of paper from setting values, such as an air flow quantity and a wind pressure, stored in an adjustment value table. Hence, it is possible to configure the same setting values with respect to a plurality of paper feed trays (that is, paper feed units) in which the same type of paper sheets are stacked. However, the setting values configured by a user cannot be reflected in the preset setting values. Therefore, even if the same type of paper sheets are stacked in a plurality of paper feed trays (that is, paper feed units), a user still has to do a troublesome work that requires a manual configuration of a setting value for each paper feed unit.
Furthermore, according to the above-described conventional techniques, the setting values may be different for different paper feed units even if the same type of paper sheets are stacked in the different paper feed units because of difference in mechanical condition such as clogging of a filter of a fan for sucking or discharging air into or from each paper feed unit. This may require change of setting value for each paper feed unit.